We introduce an AgGaGeS4 crystal for sum-frequency generation in cross-correlation frequency-resolved optical gating (XFROG) to characterize mid-IR femtosecond laser pulses between the wavelengths of 3 mu m and 11 mu m. The performance of the AgGaGeS4 crystal was examined by comparing it with a LiNbO3 crystal, which has been frequently used in the near- to mid-IR region. We can obtain XFROG images by the AgGaGeS4 crystal with efficiency 30 times greater than LiNbO3 at the wavelength of 5 mu m. (C) 2009 Optical Society of America